The present invention relates to a device and method for collecting a volume of blood or other fluids in a capillary tube for diagnostic testing. More specifically, the invention relates to a device and method for collecting a fluid sample and introducing it into a sensing device for real time analysis.
The present invention is contemplated to be used in conjunction with the disposable sensing device taught by U.S. Pat. No. 5,096,669 to Lauks, et al., the disclosure of which is herein incorporated by reference. The patent teaches a system comprising a disposable cartridge and hand-held reader for performing a variety of measurements on blood and other fluids. The disposable cartridge is constructed to serve a multiplicity of functions including sample collection and retention, sensor calibration and measurement.
A fluid sample, typically blood, is introduced into the disposable cartridge through an orifice at one end of the cartridge. The sample enters the cartridge by putting the orifice in contact with the sample. The sample is drawn by capillary action into a conduit in the cartridge, the conduit having the orifice at one end and a capillary break at the other end. After the sample fills the conduit, the orifice is sealed off. The capillary break serves to contain the sample in the conduit until the sensors of the sensing device are ready, i.e. sensor calibration is performed. When the sensors are calibrated, the sample is forced across the capillary break past the sensors by operation of an air bladder. When the air bladder is depressed, air is forced into the orifice end of the conduit which forces the sample out of the other end of the conduit past the capillary break and across the sensors, where measurements are performed.
To test, for example, a patient's blood, a phlebotomist (as used herein, the term "phlebotomist" shall include without limitation physicians, technicians, nurses and other similar personnel) may prick the patient's finger with a finger stick to draw a small amount of blood through a dermal puncture. The phlebotomist places the orifice of the cartridge on the blood formed on the dermal puncture in the patient's finger. The blood is automatically drawn into the conduit by capillary action. Blood fills the conduit up to the capillary break. Alternatively, known capillary or syringe structures may be used to collect a sample from the dermal puncture. The capillary or syringe is then transported to and put in contact with the orifice of the cartridge and the sample is deposited therein.
The sensing device disclosed in Lauks has provided the phlebotomist with the much needed capacity to obtain immediate, reliable and accurate testing of fluid samples without the processing delays associated with traditional laboratories. Moreover, the sensing device has greatly reduced the quantity of fluid sample required to be drawn from the patient's body to run these tests.
Nevertheless, experience with use of the cartridge in the hospital environment has demonstrated limitations associated with introducing fluid sample into the cartridge of the sensing device by putting the orifice in contact with the sample. Because the cartridges are not reusable, once the sample has been introduced into the cartridge through the orifice, the cartridge must be analyzed or discarded. If the sample does not fill the cartridge properly, the entire cartridge is wasted and must be discarded and a replacement cartridge must be supplied.
Another limitation associated with the prior art introduction method relates to the accuracy with which the transfer of fluid sample from the dermal puncture or the capillary tube or syringe to the orifice is made. To minimize the quantity requirement of fluid samples and to facilitate the portability of these systems, the hand held devices and disposable cartridges are designed to be small and lightweight. Research has demonstrated that phlebotomists have difficulty handling these small, lightweight cartridges. The difficulty the phlebotomists have handling the cartridge makes accurate transfers of the samples from the dermal puncture, capillary tube or syringe to the cartridge problematic. As stated above, if the sample does not fill the cartridge properly, the entire cartridge is wasted and must be discarded and a replacement cartridge must be supplied.
In addition, testing of blood includes the risk of transmission of infectious diseases such as human immunodeficiency virus or hepatitis. Therefore, any risk of spilling of blood associated with the use of the sensing device is an obvious concern.
For the foregoing reasons, there is a need for a simple disposable device to collect a volume of blood or other fluid in a capillary tube and introduce these fluids into the disposable cartridge taught by Lauks. The device should be ergonomically designed to facilitate the collection of fluid samples and the introduction of fluid samples into the cartridge. The device also should be separate and distinct from the cartridge thus allowing for sample collection errors to be remedied by discarding only the collection and introduction device rather than the entire cartridge. In addition, the device should reduce or eliminate the risk of spilling fluid samples.